For an electronic device such as a personal computer, a ZIF (Zero Insertion Force) socket (hereinafter “socket”), for example, is used for exchangably mounting a semiconductor device such as a CPU (Central Processing Unit) on a board.
FIG. 1 is a exploded perspective view showing a structure of a mounted board on which a related art socket is mounted.
Referring to FIG. 1, the mount board 1 includes a socket 2 that is mounted and fixed on a board 3 with other electronic parts. A semiconductor device 4 is mounted on the socket 2. A heat sink 5 is provided on the semiconductor device 4. A fan 6 is provided for the heat sink 5. One end of a wire of a connector 7a for connecting an electric power source for driving the fan 6 is connected to a motor (not shown in FIG. 1) for driving the fan 6. An electric power source connector 7b that is connected to the connector 7a is provided close to the socket 2 and mounted on the board 3.
The socket 2 includes two members 2-1 and 2-2 having a thin plate rectangular parallelepiped configuration. Corresponding to the rotation of the lever 2i described later, the member 2-1 slides against the member 2-2. Opening parts 2-1b and 2-2b are respectively formed in a center of main surfaces 2-1a and 2-2a of the two members 2-1 and 2-2. A terminal 3a is provided on the board 3 as facing the opening parts 2-1b and 2-2b of the members 2-1 and 2-2. A large number of first terminal receiving hole forming parts 2-1c are formed as surrounding the opening part 2-1b of the member 2-1 and facing each other.
Second terminal receiving hole forming parts 2-2c having larger diameters than the first terminal receiving hole forming parts 2-1c are formed at a position corresponding to the first terminal receiving hole forming parts 2-1c surrounding the opening part 2-1b of the member 2-1 and facing each other. Each second terminal receiving hole forming part 2-2c is connected to a contact hole forming part 3a that is formed at the board 3 so as to make a through hole. A wide end part of a contact 500 is provided at the second terminal receiving hole forming part 2-2c and the other end part of the contact 500 goes through the contact hole forming part 3a. 
A claw part 2e is provided at one side part in the X2 direction of the member 2-2 of the socket 2. Furthermore, a claw part 2f is provided at one side part in the X1 direction of the socket 2. In addition, claw parts 2g and 2h are provided at one side part in the Y1 direction of the member 2-1 so as to be off set to the Z1–Z2 direction and the X1–X2 direction. Furthermore, the lever 2i is rotatably provided at an end part of one side part in then X1 direction of the member 2-1. A head end part of the lever 2i has a step-like configuration.
The semiconductor device 4 is a PGA (Pin Grid Array) type semiconductor device. A large number of pins 4a for electric power and signals are hung down from a lower part of the semiconductor device 4 in the Z2 direction.
The fan 6 is provided at the upper part of the heat sink 5. A large number of fins 5a having long lengths in the Y1–Y2 direction stand at the heat sink 5. A groove forming part 5b is formed so as to cross through the large number of fins 5a in the X1–X2 direction. A metal fitting 5c for fixing is provided at the groove forming part 5b detachably or movably at least in the X1–X2 direction. The metal fitting 5c is formed like a plate spring so as to bend in the Z2 direction in a convex configuration. Receiving parts 5c-1 and 5c-2 having rectangular configurations and opening parts are formed at respective end parts of the metal fitting 5c. 
The mount board 1 having the above mentioned structure is assembled by the following steps.
First, the pin 4a of the semiconductor device 4 is inserted into the terminal receiving holes 2-1c and 2-2c of the socket 2 fixed at the board 3 so that the semiconductor device 4 is mounted on the socket 2. (a mounting process of the semiconductor device)
Next, the lever 2i is pushed down (rotated) so that the lever 2i is received in a space between the claw part 2g and the claw part 2h. At this time, corresponding to the rotation of the lever 2i, the member 2-1 slides against the member 2-2 due to a pushing part (not shown in FIG. 1) formed at the end part of the lever 2i so as to slightly move in the X2 direction. A head end part of the pin 4a pushed by the movement of the member 2-1 is received at the contact 500. (a pin receiving process)
Next, the heat sink 5 where the metal fitting 5c is provided is mounted on the semiconductor device 4. (a heat sink mounting process)
After that, the receiving parts 5c-1 and 5c-2 are bent in the Z2 direction so that the receiving part 5c-1 is received at the claw part 2f of the socket 2 and the receiving part 5c-2 is received at the claw part 2e of the socket 2. As a result of this, the heat sink 5 is fixed at the socket 2 with the semiconductor device 4. (a heat sink fixing process) At that time, the heat sink 5 is pressed and stands close to the semiconductor device 4 by a spring force generated by the deformation of the metal fitting 5c. 
Furthermore, the connector 7a is connected to the electric power source connector 7b. (a connector connecting process) FIG. 2 is a perspective view showing a state where the mounted board 1 shown in FIG. 1 is assembled.
However, according to the above mentioned related art, five processes, namely the mounting process of semiconductor device, the pin receiving process, the heat sink mounting process, the heat sink fixing process, and the connector connecting process are necessary for mounting the semiconductor device 4 on the above mentioned mount board 1. Hence, the assembling work for the mount board 1 is complicated so that the efficiency of the assembling work for the mount board 1 is low. In addition, there are the same problems as the assembling work for the mount board 1, in a case of analyzing and maintaining work for the exchange of the semiconductor device, for example, where the processes are implemented opposite to the assembling work for the mount board 1.